Generally, a plurality of independent control loops have been provided for managing states of a plurality of controlled subjects (end effecting devices), e.g., temperatures of heaters. Each control loop is provided with a controller, such as a PID (proportional integral differential) processor for controlling the corresponding end effecting device. In a system including a plurality of control loops, a plurality of end effecting devices may be frequently activated at the same period, thereby increasing power consumption temporarily. Therefore, high capabilities are required for a breaker and other elements arranged in each control loop.
JP-A-11-262174 discloses a temperature controller that performs time-division control wherein when one of heaters is activated, the other heaters are not activated, thereby preventing power consumption from increasing temporarily. This controller allocates one cycle among the effective periods for activating heaters in accordance with respective heating capabilities of heaters. That is, the controller allocates a shorter period to a heater that can rise the temperature quickly while allocating a longer period to a heater that rises the temperature slowly in order that all heaters enter the steady state substantially simultaneously. Accordingly, it is possible to shorten the period for waiting for the steady-state entry of the heater with a lower heating capability in a semiconductor plant or another facility where the temperature controller is installed.
However, in a sort of state management of end effecting devices, states of a plurality of end effecting devices should be frequently controlled on the basis of not only a single factor such as heating capability, but also various factors. For example, in a plant including a main control loop that needs a quick control and an auxiliary control loop that does not need it, the main control loop will be controlled preferentially. Conventional state control apparatuses are insufficient to accomplish such a complex or compound control.
The present invention may provide a state control apparatus that activates and controls a plurality of end effecting devices harmonically on the basis of a variety of factors and under restricted power consumption.